Building Realsense that works with the T261/5 module in the big 2025 is painful to say the least Since T261's software support is crap in the recent versions of librealsense, I had to build an older version of librealsense that still supports T261 and use an older version of Ubuntu to get it working.
samad@imu:~/rover$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu